Summary The most abundant endocannabinoids (eCB) in brain, 2-arachidonoyl glycerol (2-AG), is inactivated by two distinct enzymes: monoacylglycerol lipase (MAGL) and ????hydrolase domain-contain 6 (ABHD6). The selective inhibition of these enzymes increases the net levels of 2-AG in different neuronal compartments, presynaptic and postsynaptic, respectively. Accordingly, selective inhibition of these enzymes induces different spatiotemporal enhancement of 2-AG signaling and distinct or synergistic therapeutic benefits. We recently gathered results showing that ABHD6 hydrolyzes additional monoacylglycerol substrates than 2- AG and that ABHD6 inhibitors increase the net levels of 2-AG only in highly activity neurons, suggesting a novel molecular mechanism. To increase our mechanistic understanding of ABHD6 at the structural and atomic levels, we initiated an effort and have now successfully purified several functional ABHD6 protein constructs ready for structural analysis. Based on this premise, we propose the following two aims that will determine the: Aim 1: Molecular mechanisms of ABHD6 enzymatic activity. Aim 2: Structure function relationship of ABHD6. Completion of the work outline in this new R21 grant proposal will provide a comprehensive understanding of the role of ABHD6 in controlling eCB signaling in brain within the context of neurological diseases. Our long-term goal is to increase our understanding of the role played by ABHD6 in healthy and diseased brain and help develop novel therapeutics that lack the potential for abuse and adverse effects produced by classic cannabinoid agonists.